The present invention relates to a so-called bridge-type sewing machine provided with a top section carrying two needle rods which are located at a distance from each other and operated by a single shaft and with two opposite bottom sections which are located at a distance from each other and contain the lower sewing elements which cooperate with the said needle rods in order to stitch the opposite edges of articles to be made in various widths.
A sewing machine of this type, described in a pending U.S. application Ser. No. 518,279 assigned to the same Assignee as the present invention, is already known, in which the article can be freely placed in the space formed between the said bottom sections so that its opposite edges are gradually fed through under the needles mounted on the needle rods. According to the abovementioned application, it is also possible to vary the distance between the bottom sections located opposite each other, so that the article can be suitably accommodated in the said space formed between the bottom sections: for example, in the case of articles of large thickness, the distance between the bottom sections must be increased and at the same time both the needle rods and the lower sewing elements must be separated from each other by the same amount. For this purpose, provision is made, according to the abovementioned patent application, for an element which can be inserted between the two parts forming the top section of the sewing machine, in the plane of symmetry between the needle rods, such that both the needle rods and the lower sewing elements can be separated from each other by an amount equal to the thickness of the inserted element.
With this solution, a series of elements would obviously have to be inserted in order to adjust the distance between the bottom sections. This would undoubtedly give rise to a complicated procedure for obtaining correct adjustment, in addition to the inconvenience of having to keep these elements in a safe place, since, once removed, they could be misplaced.
The object of the present invention is precisely to design a sewing machine of the type described above, the features of which are such that it is possible to increase easily the distances between the bottom sections from a minimum value to a maximum value, passing through an infinite number of intermediate distances, and which is particularly efficient and practical as regards operation such that the abovementioned drawbacks can be overcome.